1. Field of the Invention
The present invention relates generally to the art of injectors. In particular, the present invention relates to a circuit for detecting failure of a fuel injector in varying states.
2. Description of the Related Art
It is known in the art of internal combustion engines that the introduction of fuel into a combustion chamber, timed in conjunction with spark plug and valve operations, can increase engine torque output. The increased torque output will result in greater power output performance of the engine. If, however, a fuel injector does not introduce fuel into the combustion chamber because of an internal failure or stays in an "on" position, engine performance can be affected. Various fuel injector failure detection circuits have accordingly been used to prevent injector operation given electrical fault or an internal injector anomaly.
Typical fuel injector failure detection circuits provide an output transistor in series connection with a solenoid fuel injector (hereinafter "fuel injector") and a current sensing resistor. In such systems a current limit controller is used to implement current control between set limits of the current flowing through the solenoid coil and output transistor. However, short circuits to ground may occur at the terminal ends of the fuel injector. This type of event can result in the sensing resistor reading that a low or zero current is flowing through the power output device and fuel injector.
Other inventions have tried to remedy the above problems by providing a fault detection circuit which can sense short circuits at either end terminal of the fuel injector. However, such inventions require the use of separate voltage comparators to monitor the voltage at each end terminal. In addition, these inventions only have the ability to detect when the terminal ends of the fuel injector are shorted to ground.
Still other inventions, which can detect the presence of a short or open circuited fuel injector, require the input of a camshaft or crankshaft sensor to determine whether the fault detection circuit has been "on" or "off" for a preselected number of degrees. Moreover, such inventions fail to read the fuel injector current at its peak rise time. This prevents early disabling of the fuel injector given a possible fault situation. In addition, such circuits do not detect a fly-back injector voltage at the end of an injector current peak time which denotes normal operation of the fuel injector.